Farm, all that's needed is to get as much dirt off the recovered bullets as you can. The rest will float out when you melt them. Just be darn sure they're dry. Best way to do it is to start a pot of them cold, then throw the heat to it. That will dry any hidden moisture out of the cracks and crannies as the pot heats up. BUT throwing a bullet with a hidden amount of water in already melted lead, will get you a visit from the tinsel fairy! The water is instantly converted to steam, if it's under the surface of the lead, it will explode coating everything in the vicinity with hot lead!

When everything is melted, toss some wax, old oil, or any other carbon based stuff in the pot and stir well. That's the flux. It'll wet the dirt to re-claim as much lead as possible. Then skim all the junk off the top. Then flux again.

As for whether the lead will be alright for casting bullets, it depends on what they were to start with. If they were good alloy when fired, they still will be. If you have some jacketed bullets in the mix, they're more like pure lead. You may have to put some harder lead in with it.

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The more people I meet, the more I love my dog

They're going to get their butts kicked over there this election. How come people can't spell and use words correctly?